From: Jingbo Xu Date: Fri, 28 Jun 2024 06:29:30 +0000 (+0800) Subject: cachefiles: add missing lock protection when polling X-Git-Tag: v6.10~20^2~4^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=cf5bb09e742a9cf6349127e868329a8f69b7a014;p=thirdparty%2Flinux.git cachefiles: add missing lock protection when polling Add missing lock protection in poll routine when iterating xarray, otherwise: Even with RCU read lock held, only the slot of the radix tree is ensured to be pinned there, while the data structure (e.g. struct cachefiles_req) stored in the slot has no such guarantee. The poll routine will iterate the radix tree and dereference cachefiles_req accordingly. Thus RCU read lock is not adequate in this case and spinlock is needed here. Fixes: b817e22b2e91 ("cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode") Signed-off-by: Jingbo Xu Signed-off-by: Baokun Li Link: https://lore.kernel.org/r/20240628062930.2467993-10-libaokun@huaweicloud.com Acked-by: Jeff Layton Reviewed-by: Jia Zhu Reviewed-by: Gao Xiang Signed-off-by: Christian Brauner --- diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c index 6465e25742309..73ed2323282a6 100644 --- a/fs/cachefiles/daemon.c +++ b/fs/cachefiles/daemon.c @@ -365,14 +365,14 @@ static __poll_t cachefiles_daemon_poll(struct file *file, if (cachefiles_in_ondemand_mode(cache)) { if (!xa_empty(&cache->reqs)) { - rcu_read_lock(); + xas_lock(&xas); xas_for_each_marked(&xas, req, ULONG_MAX, CACHEFILES_REQ_NEW) { if (!cachefiles_ondemand_is_reopening_read(req)) { mask |= EPOLLIN; break; } } - rcu_read_unlock(); + xas_unlock(&xas); } } else { if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))